Kingdom: Animalia

Phylum: Chordata

Class: Actinopterygii

Order: Tetraodontiformes

Family: Balistidae

Genus: Pseudobalistes

Species: P. flavimarginatus

Physical Description

Yellowmargin Triggerfish are pinkish to grey with a cross-hatched pattern on the sides of the body and yellow fin margins. There is a deep groove in front of the eyes and five or six rows of distinct spines on the scales on the tail base. Juveniles are yellowish with small black spots and dark saddle-like markings crossing the back.Triggerfish have a hard spine that can be locked. When sleeping this spine is used to wedge them into place in a crevasse and so deter predators from pulling them out of their bed! The spine is also held erect as a warning to other fish to stay away. Several large Titans blow shallow depressions in the sand for nesting and if approached will raise this spine as a warning.


The young of Yellowmargin Triggerfish form small aggregations when common while adults are usually seen solitary, except when nesting and males congregate on certain sand flats adjacent to reefs. Feeds on tips of coral branches, gastropods, crustaceans, foraminiferans, and tunicates and also on sea urchins. They are oviparous and Females guard the nest aggressively. During mating season, males migrate to a traditional spawning ground where they establish territories enclosing nest sites and egg chambers. Nesting occurs in sand-bottomed channels and shallow cuts through the barrier reef. The nest consist of depressions up to 2 m wide and 0.7 m deep. Females arrive several days later and select a male for mating. Exhibit biparental care. Up to 430,000 or more eggs may be deposited in a spongy fist-sized cluster weighted down with pieces of rubble

Habitat and Distribution

Inhabits coastal to inner reefs and estuaries, often in silty habitats. Found on lagoon slope and floor also coral reefs. Can be found in parts of Indo-Pacific, Red Sea south to Natal, South Africa and east through Indonesia to the Tuamoto Islands, north to southern Japan.